1. Field
One embodiment of the present invention relates to an optical recording head device, an optical recording apparatus and a recording method.
2. Description of the Related Art
A DVD (digital versatile disc) is well known as an optical disc which stores digital video. DVDs are widely used all over the world as media (digital publication products) which mainly store and distribute cinema content. Besides, optical discs having greater capacities than the DVD (referred to as “conventional DVD”) have been realized.
In the field of optical discs, there is a strong demand for a higher transfer rate as well as a larger capacity. As regards an HD DVD-R and an HD DVD-RW, 2× speed specifications, relative to standard 1× speed specifications (linear velocity=6.61 m/s), have already been published. In the near future, a further increase in transfer rate, such as 4× speed or 8× speed, is expected.
When data is recorded on an optical disc, if a peak current for obtaining a predetermined peak power is applied to a laser light source for a predetermined time period, the output intensity of the laser light source is raised to a recording power level with the application of the peak current. At the time when the output intensity of the laser light source is raised to the recording power, the intensity instantaneously rises and falls until the recording power becomes stable at a normal recording power level. This occurs due to relaxation oscillation. In usual recording pulse generation, this relaxation oscillation is controlled to decrease to a minimum.
There have conventionally been disclosed a laser driving method for recording a mark string on an optical disc by making use of the above-described relaxation oscillation, and an optical disc apparatus using this method (see Jpn. Pat. Appln. KOKAI Publication No. 2002-123963).
In the recording method disclosed in KOKAI No. 2002-123963, however, a mark string is recorded on the optical disc by making use of both ordinary recording pulses and relaxation oscillation. As regards the cycle of relaxation oscillation, this document only describes that the cycle is about 2 GHz to 4 GHz, and is silent on the relation to the physical specifications of the laser light source.